Human saliva contains several constituents that may exert antibacterial activity and that may affect the adherence of bacteria to oral tissues. Lysozyme is one constituent that is thought to act primarily as an antibacterial substance. Lysozyme may exert antibacterial activity through lytic action and also through as yet undetermined means dependent upon the extremely cationic nature of lysozyme. Lysozyme may also affect the adherence of certain bacteria to oral surfaces. The contribution lysozyme makes to the total antibacterial potency and adherence functions of saliva is unknown. We describe a technique to selectively remove ca. 95% of lysozyme from human saliva. Remaining major antibacterial substances (Lactoperoxidase, Lactoferrin, IgA) are essentially unchanged. The objective of the research proposed in this application is to determine the nature and extent of participation of salivary lysozyme to the (1) antibacterial activity and (2) bacterial adherence promoting and/or inhibiting properties of human saliva. This objective will be pursued by the comparison of unaltered salivary specimens (whole supernatant, parotid and submandibular secretions) with the corresponding lysozyme-depleted saliva specimens. Several oral and non-oral microorganisms will be used in the antibacterial studies. The relative effect of unaltered and lysozyme-depleted saliva specimens on the adherence of oral bacteria to hydroxyapatite and buccal epithelial cells will be assessed. Furthermore, the effect of unaltered and lysozyme-depleted saliva on the membrane permeability and the transport of glucose by oral and non-oral bacteria will also be evaluated. Finally, a survey of several oral bacteria will be conducted in order to determine whether oral microbes selectively absorb major salivary antibacterial constituents. The research proposed herein represents a new approach to the study of the biological role of lysozyme in saliva. The approach specified allows one to study lysozyme in the presence of the other major antibacterial and adherence factors of saliva. This approach thus, holds the added potential of uncovering interactions involving the major salivary constituents that might inhibit or promote lysozyme functions in situ.